Injection device with a spring for a needle protecting sleeve

ABSTRACT

An injection device including a housing, a needle guard sleeve displaceable relative to the housing, and a spring coupled to the guard sleeve such that the guard sleeve can be moved by the spring distally from a proximal position to an end position, the spring also being coupled to a forward drive element displaceable relative to the housing in a drive direction wherein the spring is tensioned upon a movement of the forward drive element in the forward drive direction.

CROSS-REFERENCED RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/CH2008/000288 filed Jun. 26, 2008, which claims priority toGerman Patent Application No. 10 2007 030 327.2 filed Jun. 29, 2007, theentire contents of both of which are incorporated herein by reference.

BACKGROUND

The invention relates to devices for delivering, injecting, infusing,administering or dispensing a substance, and to methods of making andusing such devices. More particularly, it relates to an injectiondevice, such as an auto-injector, for injecting a fluid product, such asa drug for diabetes or insulin therapy, wherein, after the product hasbeen successfully administered, a needle protecting sleeve associatedwith the injection device is moved or slid over the injection needle toprotect against injury.

Moving or sliding a needle protecting sleeve over a needle in the distal(forward) direction, from its proximal (rearward) position in which theneedle is exposed, by using a spring, such that the needle is protectedagainst being accessed from without, is known from the prior art. Thespring which charges the needle protection with a spring force is biasedby an amount in the proximal position of the needle protecting sleeve.When the needle protecting sleeve is advanced beyond the injectionneedle, the spring force decreases according to the rules of Hooke'sLaw. The bias on the spring therefore has to be selected such that theneedle protecting sleeve can reliably assume the end position in whichit covers the injection needle.

Shifting the needle protecting sleeve from a distal position into theproximal position beforehand, to bias the spring, is also known. Duringthis movement, mechanical switching processes of parts which are coupledto the needle protecting sleeve are performed as applicable. To effectthese switching processes, additional forces which act on the needleprotecting sleeve in the proximal direction are needed, in addition tothe force needed to bias the spring, to shift the needle protectingsleeve in the proximal direction. It is, however, desirable to keep thetotal force needed to shift the needle protecting sleeve in the proximaldirection low, to make it easier for the user to handle the device. Onthe other hand, as stated above, increased spring forces are desirablefor shifting the needle protecting sleeve in the distal direction fromthe proximal position.

SUMMARY

It is therefore one object of the present invention to provide aninjection device and a method in which the spring force driving theneedle protecting sleeve can be adapted in accordance with theadministering process.

In one embodiment, the present invention comprises an injection devicecomprising a housing, a needle guard sleeve displaceable relative to thehousing, and a spring coupled to the guard sleeve such that the guardsleeve can be moved by the spring distally (forward) from a proximal(rear) position to an end position, the spring also being coupled to adrive element displaceable relative to the housing in a forward drivedirection wherein the spring is tensioned upon a movement of the driveelement in the forward drive direction.

In one embodiment, the present invention comprises an injection devicefor administering a fluid product. The fluid product can, for example,be insulin or a hormone or other drug. The injection device can beembodied as a simple injection device, e.g. an injection needle formedon or carried by the injection device is injected manually.Alternatively, the injection device can be embodied as an auto-injector,generally wherein the injection needle is injected by an injectionmechanism, and wherein the product is delivered via a delivery mechanismonce the injection needle has been injected.

In one embodiment, the present invention comprises an injection devicewith a housing. A needle guard sleeve, which is displaceable relative tothe housing, is coupled to a spring in such a way that the needle guardsleeve can be moved distally from a proximal position to an end positionwith the spring. The spring is coupled to a forward drive element, whichis displaceable relative to the housing, in such a way that it can betensioned upon a movement of the forward drive element in the forwarddrive direction.

In some embodiments, the injection device comprises a housing. Thehousing can comprise one part or multiple parts, for example it maycomprise a proximal housing part and a distal housing part which islatched, axially fixed, to the proximal housing part. A multiple-parthousing offers advantages when assembling the injection device.

In some embodiments, the injection device also comprises an activatingelement which can be shifted relative to the housing and which may bethought of and/or referred to as a needle protecting sleeve or needlecover. The activating element can be able to be moved along thelongitudinal axis of the housing which is, for example, cylindrical,between distal (forward) and proximal (rearward) positions. In somepreferred embodiments, the activating element can at least be shiftedfrom an activating position, e.g. a proximal position, in which theactivating element is activated, in the distal direction, into an endposition. In some preferred embodiments, the activating element canadditionally be shifted proximally from an initial position into theactivating position. The initial position and the end position can, butneed not, be identical. In the end position, the activating elementassumes a more distal position than in the initial position. In its endposition, the activating element protrudes distally beyond the distalend of the housing, wherein for example the activating element protrudesdistally beyond the distal end of the housing by a greater amount in itsend position than in its initial position. When the activating elementprotrudes distally beyond the distal end of the housing, itsimultaneously forms the distal end of the injection device. Asapplicable, the activating element also protrudes distally beyond thedistal end of the housing in its initial position. It can, for example,be able to be moved from this position into the activating position.

In some preferred embodiments, the activating element in the endposition protrudes beyond the distal end of the injection needle formedon the injection device. This prevents access to the injection needleand reduces the danger of injury. The activating element can alsoprotrude beyond the distal end of the injection needle in the initialposition. Alternatively, the distal end of the injection needle canprotrude beyond the distal end of the activating element in the initialposition of the activating element. The injection needle can protrudebeyond the distal end of the injection device in the activating positionof the activating element. In this position, the distal end is formed bythe distal end of the housing and/or by the distal end of the activatingelement. When the activating element is situated in the activatingposition, the injection needle can protrude or be advanced far enoughbeyond the distal end of the injection device that the needle lengthwhich protrudes beyond the distal end of the injection devicecorresponds to the injection depth. The activating element is designedto be placed onto an injection location provided on the patient. Whenthe placed injection device is pressed onto the injection location, theactivating element is shifted from the initial position into theactivating position, i.e. into the proximal position in this case; thiscan be thought of as activating the activating element. The activatingelement can be designed to indicate, to the mechanism for injecting theinjection needle or delivering the product, i.e. for example to effect amechanical switch, that the injection device has been properly placedonto the injection location and the needle injected. In some preferredembodiments, the activating element is a needle protecting or coveringsleeve which can reduce access to the needle and therefore the danger ofinjury.

In some preferred embodiments, an injection device in accordance withthe present invention also comprises a spring, such as a restoringspring, wherein the spring is coupled to the activating element suchthat the activating element can be shifted from the activating positioninto the end position using and/or by the spring. The spring can be atension spring or a pressure spring. Plastics or metals, for examplespring steel, are materials which may be considered for the spring. Insome preferred embodiments, the spring is helical. Instead of a spring,other spring elements can also be used. The spring elements obey Hooke'sLaw, although this is not absolutely necessary for the injection deviceto function. The spring can be directly or indirectly coupled to theactivating element. If directly coupled, the spring is supported on theactivating element. In some preferred embodiments, the distal end of thespring is supported on the activating element, and the other end can besupported on an advancing member. If the spring is indirectly coupled tothe activating element, the activating element can be coupled via anelement which is connected to the activating element and on which thespring is supported. Such an element can, for example, be a transferelement. The activating element and the transfer element can beconnected, axially fixed, to each other. In some embodiments, at leastthe activating element and the transfer element can respectivelytransfer a pressure force onto the other.

In some embodiments, the advancing member can be shifted relative to thehousing in an advancing direction, e.g. an injection direction, adelivery direction or distal direction. In some embodiments, the springis coupled to the advancing member such that it can be tensed when theadvancing member moves in the advancing direction. By tensing thespring, the movement of the advancing member in the advancing directionincreases the spring force and therefore the force which acts on theactivating element, such that an increased force then acts on theactivating element, whereas initially a small force acts on theactivating element. The initially small force is desirable foractivating the activating element, i.e. moving the activating elementinto its activating position and/or in the proximal direction. Thiskeeps the spring force small as a portion of the total force required toactivate the activating element, which can also include switching forcesor frictional forces. The increased force after the advancing member hasbeen shifted is desirable to move the activating element completely andreliably from its activating position into its end position. In somepreferred embodiments, in its end position, the activating element islatched, axially fixed, relative to the housing. The increased springforce is likewise advantageous for establishing this latchingconnection, which can be established between the housing and theactivating element, since it enables it to reliably latch in. Thelatching reduces the danger of injury even further, since the activatingelement is prevented from being inadvertently retracted, which wouldcause the injection needle to protrude.

In some embodiments, a device in accordance with the present inventionalso comprises another spring, an advancing spring for moving theadvancing member in the advancing direction. The advancing spring cantense the spring of the activating element, which is then referred to asthe restoring spring to better distinguish it. in some preferredembodiments, the advancing spring is biased heavily enough that itexhibits a greater spring force than the restoring spring. In someembodiments, the bias on the advancing spring should be selected suchthat the force of the advancing spring is greater than the force of therestoring spring in all the switching positions of the injection device.

In some embodiments, the injection device also comprises a productcontainer generally associated with the housing. The product containercan be formed by the housing itself or by a separate product containerwhich is or can be inserted into the housing, e.g. an ampoule. At oneend, the product container is or can be connected to the injectionneedle, e.g., the injection needle is or can be fastened directly to theproduct container. At the other end, the proximal end, the productcontainer comprises an opening which is sealed by a piston which isarranged in the product container. The piston can be shifted relative tothe product container to deliver product, such that the product situatedbetween the piston and the opposite end of the product container isdelivered due to the movement of the piston. The advancing member can becoupled to the piston which is arranged in the product container, suchthat the piston can be shifted relative to the housing of the injectiondevice by the advancing member. The advancing member can thus act on thepiston indirectly, such as via the product container or directly.

In some preferred embodiments, when the activating element moves fromthe initial position into the activating position or proximal position,the restoring spring can be tensed by a first distance, and when theadvancing member moves in the distal direction from its initialposition, such as for example its proximal position, the restoringspring can be tensed by a second distance, in addition to the firstdistance. In some preferred embodiments, the first distance isproportional to a first amount of change in the spring force, and thesecond distance is proportional to a second amount of change in thespring force. The force acting on the activating element thus amounts toat least the sum of the first amount and the second amount, wherein theoriginal bias on the spring is also added.

In a preferred embodiment, the advancing member is a piston rod whichneed not necessarily be solid, but may be rather sleeve-shaped, i.e. atleast partially hollow and/or cylindrical. The piston can be shiftedrelative to the product container using the advancing member. In someembodiments, the needle is injected manually into the patient. Theadvancing spring, which in this case is a delivery spring, can forexample be supported on the housing or on an element which is fixed withrespect to the housing, and on the piston rod. Furthermore, therestoring spring can be supported on the piston rod or on an elementwhich is connected, axially fixed, to it, and on the activating element.This relaxes the delivery spring for advancing the piston during aproduct delivery, wherein the restoring spring is simultaneously tensedby the delivery spring. A triggering element can be provided whichreleases a blocking connection, which prevents the piston rod frommoving in the delivery direction due to the biased delivery spring, suchthat a delivery movement can be performed. In some embodiments, theactivating element has to be activated in addition to the triggeringelement to enable the blocking connection to be released. The elementsare correspondingly coupled to each other.

In another preferred embodiment, the injection device is anauto-injector. The advancing member can be an advancing element usingwhich the entire product container can be shifted relative to thehousing. Shifting the product container in an injection direction, i.e.the distal (forward) direction, enables the injection needle to protrudefrom the distal end of the injection device to be injected into thepatient. The product container can be shifted distally from an initialposition into an end position. In the end position, the injection needleprotrudes distally beyond the distal end of the injection device. In theinitial position of the product container, the injection needle does notprotrude beyond the distal end of the injection device, i.e. the distalend of the needle is situated proximally with respect to the distal endof the injection device.

In some embodiments, the advancing element can be shifted in theinjection direction by the advancing spring which serves as an injectionspring. The advancing element can charge the product container with anadvancing force, at least in the distal direction. The product containercan be held in a product container holder which can be moved togetherwith the product container in the injection direction. In some preferredembodiments, the advancing spring is supported on the housing or on anelement which is connected, axially fixed, to the housing, and on theadvancing element or an element which is connected, axially fixed, tothe advancing element. The advancing element is latched, axially fixed,relative to the housing in a position in which the product container issituated in its initial position. When this latching connection isreleased, the advancing element is released for an advancing movement.As long as the latching connection exists, the advancing spring is in atensed state, wherein when the latching connection is released, therestoring spring can be relaxed and the advancing element thus moves inthe advancing direction and simultaneously tenses the restoring springby an amount, by the second amount. The latching connection by which theadvancing element is held can be released when a triggering element suchas a triggering button is activated, in combination with activating theactivating sleeve, thus enabling the restoring spring to be biased by afirst amount.

In some embodiments, the injection device comprises a piston rod whichcan be shifted relative to the advancing element. Furthermore, thepiston can be able to be shifted by the piston rod relative to theproduct container. The injection device comprises a releasing memberwhich can block, lock or prevent the relative movement between thepiston rod and the advancing element. The releasing member blocks therelative movement between the piston rod and the advancing elementduring the injection movement. A switching ring can be provided whichreleases the releasing member at the end of the injection movement ormoves it out of engagement with the piston rod or at least enables thereleasing member to be released, such that the piston rod can perform adelivery movement. For advancing the piston rod, i.e. for the deliverymovement, i.e. when the piston rod is to be moved relative to theadvancing element, a delivery spring is provided which acts on thepiston rod. The piston rod can be sleeve-shaped, wherein the deliveryspring can be situated in the sleeve-shaped piston rod, in a biasedstate. The advancing spring can be supported on the piston rod and on anelement which is fixed with respect to the housing or on the advancingelement or on an element which is connected, axially fixed, to theadvancing element.

In some embodiments, the present invention comprises a method foroperating an injection device, wherein an advancing member for aninjection movement and a product delivery is moved in the distaldirection relative to a housing and thereby tenses a spring, e.g. arestoring spring, which acts on an activating element, wherein theactivating element is shifted distally by the tensed spring from theproximal position into an end position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are sectional views of an embodiment of an injectiondevice in accordance with the present invention in an initial position,wherein FIG. 1B is the view from FIG. 1A rotated about the longitudinalaxis by 90°;

FIGS. 2A and 2B are sectional views of the injection device of FIGS. 1Aand 1B, comprising an activating sleeve which is situated in anactivating position, wherein FIG. 2B is the view from FIG. 2A rotatedabout the longitudinal axis by 90°;

FIGS. 3A and 3B are sectional view of the injection device of FIGS. 1Aand 1B in an injection position, wherein FIG. 3B is the view from FIG.3A rotated about the longitudinal axis by 90°.

DETAILED DESCRIPTION

With regard to fastening, mounting, attaching or connecting componentsof the present invention, unless specifically described as otherwise,conventional mechanical fasteners and methods may be used. Otherappropriate fastening or attachment methods include adhesives, weldingand soldering, the latter particularly with regard to the electricalsystem of the invention, if any. In embodiments with electrical featuresor components, suitable electrical components and circuitry, wires,wireless components, chips, boards, microprocessors, inputs, outputs,displays, control components, etc. may be used. Generally, unlessotherwise indicated, the materials for making embodiments of theinvention and/or components thereof may be selected from appropriatematerials such as metal, metallic alloys, ceramics, plastics, etc.Unless otherwise indicated specifically or by context, positional terms(e.g., up, down, front, rear, distal, proximal, etc.) are descriptivenot limiting. Same reference numbers are used to denote same parts orcomponents.

FIGS. 1A and 1B show an injection device which is embodied as anauto-injector. The injection device comprises a housing 1 which isformed from a distal housing part 1 b and a proximal housing part 1 a.The distal housing part 1 b is latched, axially fixed, to the proximalhousing part 1 a and cannot be directly released by the user.Configuring the injection device in two parts has the advantage thateasier assembling is possible. The distal housing part 1 b, mounts (orcarries) an activating element which is embodied as a needle protectingsleeve 6, such that it can be axially shifted, i.e. such that the needleprotecting sleeve 6 can be shifted along the longitudinal axis L of theinjection device. The injection device is shown in FIGS. 1A and 1B witha needle protecting sleeve 6 situated in its initial position. In theinitial position, the needle protecting sleeve 6 protrudes beyond thedistal end of the distal housing part 1 b. As shown in this example, theneedle protecting sleeve 6 protrudes by the amount “s”. The distal endof an injection needle 13 which is surrounded by the housing 1 issituated proximally with respect to the distal end of the needleprotecting sleeve 6 and, as shown in this case, also proximally withrespect to the distal end of the distal housing part 1 b. Thus, evenwhen the needle protecting sleeve 6 is shifted in the proximal directionby the distance “s”, the distal end of the injection needle 13 does notprotrude beyond the distal end of the injection device (FIGS. 2A and2B), i.e. in the activated position of the needle protecting sleeve 6,the tip of the injection needle is protected against being inadvertentlyaccessed.

The needle protecting sleeve 6 is designed to be placed onto aninjection location on a patient. When the placed injection device ispressed onto the patient, the needle protecting sleeve 6 is activated,i.e. shifted in the proximal direction, wherein a transfer element 12which abuts the proximal end of the needle protecting sleeve 6 is slavedby the same distance “s” as the distance by which the needle protectingsleeve 6 is shifted, and is therefore likewise moved relative to thehousing 1.

A collar 12 a which protrudes radially inward and on which the distalend of a spring 9 is supported is formed on the transfer element 12. Theproximal end of the spring 9 is supported on a collar 11 a which pointsradially outward and is formed on an advancing element 11 which servesas the advancing member. Thus, when the needle protecting sleeve 6 ismoved into its activating position, the spring 9 is biased by a firstamount by the movement of the transfer element 12 by the first distance.If, for example, the needle protecting sleeve 6 is moved in the proximaldirection by the distance “s”, then the spring 9 is biased by an amountwhich is dependent on the distance “s”. The resultant spring force maybe ascertained using Hooke's Law.

When the user removes the injection device from the injection location,the needle protecting sleeve 6 is retracted by the spring 9 back intoits initial position, as shown for example in FIGS. 1A and 1B, since aninjection movement has not yet been performed.

The proximal end of the transfer element 12 comprises a blocking member12 b which engages with a blocking groove and thus prevents the needleprotecting sleeve 6 from moving any further in the distal direction thanas shown in FIGS. 1A and 1B. The blocking groove is distally restrictedby an element which is fixed with respect to the housing, e.g. a cage 2,and proximally restricted by a cam surface 14 a which is formed by atriggering element 14. The triggering element 14 serves to trigger theinjection device to administer the product. In the position shown inFIG. 1B, the triggering element 14 cannot be pressed, since the cage 2comprises an undercut 2 a which prevents the blocking member 12 b fromunlatching by moving radially outward. The cam surface 14 a cannottherefore press the blocking member 12 b radially outward, out of theblocking groove, despite exerting a pressure on the triggering element14. If the needle protecting sleeve 6 as shown in FIGS. 2A and 2B ismoved in the proximal direction by the distance “s”, the blocking member12 b is also moved in the proximal direction and is thus pressedradially outward, out of the blocking groove, by the cam surface 14 a ofthe triggering element 14. The triggering element 14 is thus releasedfor a triggering movement, i.e. for a movement in the distal direction.When the triggering element 14 is moved in the triggering direction, asnap-on connection 17—which prevents the advancing element 11 frommoving in the distal direction, i.e. in the injection direction—isreleased, such that the advancing element 11 can be moved in theinjection direction. Once the triggering element 14 has been activated,it latches—axially fixed—to the cage 2, as shown in FIG. 3B, andalternatively to the housing 1, such that the blocking groove for theblocking member 12 b is sufficiently closed that the blocking member 12b can no longer latch in between the cam surface 14 a and the undercut 2a.

Since the advancing element 11 is released for a movement in the distaldirection after the triggering element 14 has been activated, a biasedinjection spring 7 which serves as the advancing spring can move theadvancing element 11 in the delivery direction. The advancing element 11is latched, axially fixed, to a supporting element 11 b, such that thetwo parts behave as a single part. The division into two parts may beexpedient for assembling reasons. The distal end of the advancing spring7 is supported on a collar which points radially outward and is formedon the supporting element 11 b, and the proximal end of the advancingspring 7 is supported on the cage 2. The advancing spring 7 surroundsthe transfer element 12 and the advancing element 11, as shown forexample in FIG. 1B. Driven by the advancing spring 7, the advancingelement 11 is moved in the delivery direction together with a piston rod10 accommodated in it, wherein the spring 9 is tensed by a second amountwhich is dependent on the distance “u”, in addition to the first amountwhich is dependent on the distance “s”. This increases the spring forceof the spring 9.

The advancing element 11 is coupled to a product container 3 via thesupporting element 11 b, such that when moving in the deliverydirection, it can likewise slave the product container 3 in the deliverydirection. In particular, the distal end of the supporting element 11 babuts the proximal end of the product container 3. The product container3 is held in a product container holder 5. The product container 3 isheld axially fixed relative to the product container holder 5. Theproduct container holder 5 serves as an axial guide for the productcontainer 3. The injection needle 13 is fastened to the distal end ofthe product container 3. The injection needle 13 is fluidicallyconnected to the interior of the product container 3. A piston 4 isarranged at the proximal end of the product container 3 and can be movedrelative to the product container 3. When the piston 4 is moved in thedirection of the injection needle 13, the product is delivered throughthe injection needle 13.

During the injection movement of the advancing member 11, the productcontainer 3 and therefore the injection needle 13 is shifted in thedistal direction, wherein the injection needle 13 protrudes distallybeyond the distal end of the injection device, as shown in FIGS. 3A and3B. The distance which the injection needle 13 protrudes corresponds tothe injection depth into the tissue of the patient.

Before an injection movement has been completely performed, the pistonrod 10 which is surrounded by the advancing element 11 is connected,axially fixed, to the advancing element 11. This means that the pistonrod 10 participates in the advancing movement of the advancing element11, wherein no relative movement between the advancing element 11 andthe piston rod 10 is performed. The releasing member 16 a is responsiblefor arranging the piston rod 10 axially fixed relative to the advancingelement 11. The releasing member 16 a is formed on a functional sleeve16 which is arranged between the piston rod 10 and the advancing element11. The releasing member 16 a is elastically connected to the functionalsleeve 16 via an elastic arm or integrally formed with it. In theswitching positions shown in FIGS. 1A, 1B, 2A and 2B, a protrusion ofthe releasing member 16 a which is directed radially inward engages witha collar or heel which is circumferentially formed on the outer surfaceof the piston rod 10. This prevents the piston rod 10 from moving in thedistal direction relative to the advancing element 11. The side of thereleasing member 16 a which points radially outward exhibits a conicalsurface which co-operates with a correspondingly counteracting conicalsurface of the supporting element 11 b which is directed radiallyinward. The surface of the supporting element 11 b which is directedradially inward prevents the releasing member 16 a from unlatching fromthe engagement with the piston rod 10, by preventing the releasingmember 16 a from moving outward in the radial direction.

The injection device also features a switching element 15 which can bemoved relative to the supporting element 11 b by a distance “x”, asshown in FIG. 1B. The switching element 15 comprises an abutment surface15 a which can be moved into axial abutment with an abutment 1 c formedby the housing 1, e.g. by the distal housing part 1 b. At the end of theinjection movement, the switching element 15 is pressed against theabutment 1 c by the injection spring 7. This holds the switching element15 axially fixed with respect to the housing 1, while the injectionspring 7 slides the supporting element 11 b further in the distaldirection, thus shifting the supporting element 11 b relative theswitching element 15 by the distance “x”, i.e. by a switching distance.FIG. 3B shows the position of the supporting element 11 b and theswitching element 15 relative to each other. As likewise shown in FIG.3B, there is then a radial gap between the supporting element 11 b andthe releasing member 16 a, such that the releasing member 16 a canunlatch, radially outwardly, from the engagement with the piston rod 10.The piston rod 10 is then released for a movement in the deliverydirection, i.e. the distal direction.

The piston rod 10 is formed as a sleeve in which a delivery spring 8 isarranged for driving the piston rod 10 relative to the advancing element11 and/or for a product delivery. The distal end of the delivery spring8 is supported on a distally formed end-facing surface of the piston rod10, and the proximal end of the delivery spring 8 is supported on theadvancing element 11 or an element which is formed, axially fixed, withthe advancing element 11, or alternatively on the functional sleeve 16or on an element which is formed axially fixed with respect to thefunctional sleeve 16. After the piston rod 10 has been released, e.g.after an injection movement has been completely performed, the biaseddelivery spring 8 drives the piston rod 10 in the delivery direction.The distal end of the piston rod 10 acts on the piston 4, such that itis slaved in the distal direction and causes the product to bedelivered.

In some preferred embodiments, the springs described herein are pressuresprings and embodied to be helical. The springs are in particular madeof a suitable metallic material, e.g. spring steel, a plastic, etc. Theinjection spring 7 is biased and/or selected such that in its mostrelaxed state, it exhibits a spring force which is greater than or atleast as great as the spring 9 in its most tensed state, in somepreferred embodiments, after it has been biased by the first amount andthe second amount.

After the product has been successfully delivered (not shown in thefigures), the user of the device removes the injection device from theinjection location. This then shifts the needle protecting sleeve 6 inthe distal direction, due to the spring 9 which is biased by the firstdistance “s” and the second distance “u”, with a force which is greaterthan the force which was required to shift the needle protecting sleeve6 by the distance “s” from the position shown in FIG. 1B into theposition shown in FIG. 2B. Since the blocking groove between the cage 2and the triggering element 14 for latching in the blocking member 12 bis then sealed (see FIG. 3B), the transfer element 12 and therefore alsothe needle protecting sleeve 6 can be shifted in the distal direction bya distance which is greater than the distance “s” by which the needleprotecting sleeve 6 was shifted in the proximal direction from theposition shown in FIG. 1B. The needle protecting sleeve 6 is shifted farenough in the distal direction that its distal end protrudes distallybeyond the distal end of the injection needle 13. In this respect, it ispreferred in some embodiments if, as shown in FIG. 3A, a gap “y” betweena locking cam 6 a formed radially outward on the needle protectingsleeve 6 and an axial abutment formed by the housing 1, e.g. by thedistal housing part 1 b, is correspondingly selected. When the needleprotecting sleeve 6 moves in the distal direction, the locking cam 6 aabuts the axial abutment formed by the housing 1. In this position, theneedle protecting sleeve 6 is situated in its end position in which itcompletely covers the injection needle 13. When the locking cam 6 amoves by the distance “y”, it crosses a locking tongue 1 d formed by thehousing 1, e.g. by the distal housing part 1 b. The locking tongue 1 dcan spring radially outward and is integrally formed on the distalhousing part 1 b. Once the locking cam 6 a has crossed the lockingtongue 1 d, the locking tongue 1 d springs radially inward, such thatits distal abutment surface is braced against the proximal side of thelocking cam 6 a. The needle protecting sleeve 6 is then blocked againstmoving in the proximal direction, such that the needle 13 can no longerbe released. In other words, the needle protecting sleeve 6 latches,axially fixed, to the housing 1. The needle protecting sleeve 6 servesas a needle protection and reduces the danger of injury to personshandling the injection device. The used injection device can then besecurely disposed of.

Embodiments of the present invention, including preferred embodiments,have been presented for the purpose of illustration and description.They are not intended to be exhaustive or to limit the invention to theprecise forms and steps disclosed. The embodiments were chosen anddescribed to illustrate the principles of the invention and thepractical application thereof, and to enable one of ordinary skill inthe art to utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variations are within the scope of the invention asdetermined by the appended claims when interpreted in accordance withthe breadth they are fairly, legally, and equitably entitled.

The invention claimed is:
 1. An injection device comprising: a) ahousing enclosing a product container connected to an injection needle;b) an activating element shiftable relative to the housing from aninitial position in which the activating element protects the injectionneedle to a proximal position to permit manual injection of theinjection needle; (c) an advancing member shiftable relative to thehousing in an advancing direction, said advancing member comprising ahollow piston rod with a delivery spring fixed thereon, said piston rodacting on a piston to shift it relative to the product container; d) arestoring spring for shifting the activating element distally from theproximal position to an end position; wherein e) the restoring springhas one end supported on the activating element and another endsupported on an element connected to the piston rod, such that therestoring spring is tensed by a first amount when the activating elementmoves from the initial position to the proximal position, and themovement of the advancing member in the advancing direction, driven byrelaxation of the delivery spring, simultaneously advances the pistonrod for product delivery and moves the element connected to the pistonrod in a direction that increases the tension in the restoring spring tocause a force greater than the force initially acting on the activatingelement.
 2. The injection device according to claim 1, wherein in itsend position, the activating element protrudes distally beyond a distalend of the housing.
 3. The injection device according to claim 1,wherein the activating element is a needle protecting sleeve which inits end position protrudes beyond the distal end of an injection needlecarried by the injection device.
 4. The injection device according toclaim 1, wherein the activating element is moveable in the proximaldirection from the initial position, in which the activating elementprotrudes distally beyond the distal end of the housing, to the proximalposition which comprises an activating position.
 5. The injection deviceaccording to claim 4, wherein the restoring spring is tensed by a secondamount based on a distance the advancing member moves in the advancingdirection from an initial position.
 6. The injection device according toclaim 5, wherein in its end position, the activating element protrudesdistally beyond the distal end of the housing by a greater amount thanin its initial position.
 7. The injection device according to claim 1,wherein in its end position, the activating element is latched, axiallyfixed, relative to the housing.
 8. The injection device according toclaim 1, wherein the piston arranged in the product container can beshifted relative to the housing by the advancing member.
 9. Theinjection device according to claim 8, wherein the advancing membercomprises an advancing element by which the product container can beshifted relative to the housing.
 10. The injection device according toclaim 9, wherein the product container can be shifted distally from aninitial position into an end position, wherein in the end position, theinjection needle arranged on the product container protrudes distallybeyond the distal end of the injection device.
 11. The injection deviceaccording to claim 10, wherein the piston rod can be shifted relative tothe advancing element.
 12. The injection device according to claim 11,further comprising a releasing member which can block the relativemovement between the piston rod and the advancing element.
 13. A methodfor operating an injection device, said device comprising: a) a housingenclosing a product container connected to an injection needle; b) anactivating element shiftable relative to the housing from an initialposition to a proximal position to permit manual injection of theinjection needle; (c) an advancing member shiftable relative to thehousing in an advancing direction, said advancing member comprising ahollow piston rod with a delivery spring fixed thereon, said piston rodacting on a piston to shift it relative to the product container; d) arestoring spring for shifting the activating element distally from theproximal position to an end position; wherein e) the restoring springhas one end supported on the activating element and another endsupported on an element connected to the piston rod, such that therestoring spring is tensed by a first amount when the activating elementmoves from the initial position to the proximal position, wherein thedelivery spring shifts the advancing member for product injectionmovement or a product delivery in an advancing direction relative to ahousing and thereby simultaneously tenses the restoring spring toincrease the tension in the restoring spring to cause a force greaterthan the force initially acting on the activating element, wherein theactivating element is shifted by the tensed spring from an activatingposition into an end position.
 14. The method of claim 13, wherein whenthe activating element is shifted by the tensed spring into an endposition, it is latched, axially fixed, relative to the housing.
 15. Themethod of claim 13 wherein the activating element is a needle protectingsleeve.
 16. The method of claim 13 further comprising, pressing theinjection device against the patient activates the needle protectingsleeve to enable manual injection of the needle.
 17. The method of claim13 further comprising, activating a triggering element to release ablocking connection that prevents the piston rod from moving in adelivery direction.